In an ion exchange membrane electrolyzer used for chlorine-alkaline electrolysis, three components of the ion exchange membrane electrolyzer, which are an anode, an ion exchange membrane and a hydrogen-generating cathode, are normally arranged in close contact with each other to promote reduction in electrolysis voltage. However, in a large-scale electrolyzer which attains as much as several square meters of electrolysis area, when an anode and a cathode made of a rigid member were accommodated in the electrolyzer, it was difficult to maintain the distance between the electrodes at a determined value, with both electrodes brought into close contact with an ion exchange membrane.
An electrolyzer is known in which an elastic material is employed on an item used as a means to reduce the distance between electrodes or between an electrode and a current collector or as a means to maintain the distance between them at a nearly constant value. Such an electrolyzer has a structure in which at least one of the electrodes moves freely in the direction from one electrode to the other in order to avoid breakage of an ion exchange membrane by uniformly close contact of the electrode with the ion exchange membrane and to maintain the minimum distance between the anode and the cathode, and the pinch pressure is controlled by pressing the electrode through the elastic member. Non-rigid materials such as woven fabric, non-woven fabric, mesh and the like, which are formed of a metal fine wire; and rigid materials such as leaf spring and the like are known as examples of this elastic material.
However, conventional non-rigid materials had disadvantages. For example, when excessive pressure is applied to a conventional non-rigid material from the anode side after attaching it to an electrolyzer, the non-rigid material is partially deformed to have a non-uniform distance between electrodes and/or an ion exchange membrane is pricked with a fine wire of the non-rigid material. Moreover, rigid materials such as leaf spring and the like had disadvantages. For example, a rigid material damages an ion exchange membrane and/or causes plastic deformation of an ion exchange membrane so that the ion exchange membrane cannot be reused. Furthermore, for an ion exchange membrane electrolyzer such as a brine electrolyzer, the close proximity of an anode and/or a cathode to an ion exchange membrane is preferred to allow continuous operation of the electrolyzer at a low voltage and therefore various methods to press an electrode toward an ion exchange membrane are proposed.
For example, Patent Document 1 proposes an electrolyzer in which a metal coil body instead of a conventionally used leaf spring or metal mesh body is installed between a cathode and a cathode end plate and the cathode is uniformly pressed toward a barrier membrane to bring each member into close contact with the barrier membrane. However, a metal coil body has a high deformation ratio and therefore is difficult to handle and often causes difficulty in installation to a determined part of an electrolyzer in accordance with a worker's intention. Moreover, a metal coil body is easily deformed (its strength is insufficient) and it sometimes causes difficulty in uniformly close contact between respective members due to deviation of the metal coil body by an electrolyte and/or generated gas in an electrolyzer even if the metal coil body is once installed to a determined part of the electrolyzer.
In order to address such an issue, Patent Document 2 proposes an ion exchange membrane electrolyzer, in which an elastic cushion member (20) instead of a metal coil body is installed between a hydrogen-generating cathode and a cathode current collecting plate and the hydrogen-generating cathode is uniformly pressed toward an ion exchange membrane, wherein this elastic cushion member (20) is prepared as shown in FIG. 5b by winding a metal coil body (22) around a rectangular corrosion-resistant frame (21) as shown in FIG. 5a so as to provide a nearly uniform density.